Re: [Qemu-devel] [PATCH v2] Change the method to calculate dirty-pages-rate

[Juan Quintela <quintela@redhat.com>]

Chao Fan <fanc.fnst@cn.fujitsu.com> wrote:
> In function cpu_physical_memory_sync_dirty_bitmap, file
> include/exec/ram_addr.h:
>
> if (src[idx][offset]) {
>     unsigned long bits = atomic_xchg(&src[idx][offset], 0);
>     unsigned long new_dirty;
>     new_dirty = ~dest[k];
>     dest[k] |= bits;
>     new_dirty &= bits;
>     num_dirty += ctpopl(new_dirty);
> }
>
> After these codes executed, only the pages not dirtied in bitmap(dest),
> but dirtied in dirty_memory[DIRTY_MEMORY_MIGRATION] will be calculated.
> For example:
> When ram_list.dirty_memory[DIRTY_MEMORY_MIGRATION] = 0b00001111,
> and atomic_rcu_read(&migration_bitmap_rcu)->bmap = 0b00000011,
> the new_dirty will be 0b00001100, and this function will return 2 but not
> 4 which is expected.
> the dirty pages in dirty_memory[DIRTY_MEMORY_MIGRATION] are all new,
> so these should be calculated also.
#
> Signed-off-by: Chao Fan <fanc.fnst@cn.fujitsu.com>
> Signed-off-by: Li Zhijian <lizhijian@cn.fujitsu.com>
>
> ---
> v2: Remove the parameter 'num_dirty_pages_init'
>     Fix incoming parameters of trace_migration_bitmap_sync_end

Reviewed-by: Juan Quintela <quintela@redhat.com>

Just curious, does this change show any difference in any load?

Later, Juan.